synthesis and purity assessment of eactive dyes -...
TRANSCRIPT
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Chapter 2
SYNTHESIS AND PURITY ASSESSMENT OF REACTIVE
DYES CONTENTS
2.1 INTRODUCTION 27
2.1.1 General Synthesis of Reactive Dyes with Azo
Chromophore
2.2 MATERIALS AND INSTRUMENTATION 33
2.3 LABORATORY SCALE SYNTHESIS 33
2.3.1 Synthesis of Reactive Red A
2.3.2 Synthesis of Reactive Red B
2.3.3 Synthesis of Reactive Red C
2.3.4 Synthesis of Reactive Orange D
2.3.5 Synthesis of Reactive Black BE
2.4 SCALED-UP SYNTHESIS FOR MANUFACTURING PLANT 46
2.5 PURITY ASSESSMENT OF DYES BY HPLC 49
2.6 CONCLUSIONS 52
2.7 REFERENCES 52
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2.1 Introduction
Reactive dyes, as their name implies, chemically react with the fiber to form a
strong linkage that gives rise to high performance to wet treatments such as laundering.
This class of dyes, first introduced commercially in 1956 by ICI, made it possible to
achieve extremely high wash fastness properties by relatively simple dyeing methods.
Today they are the largest single range of dyes used for the dyeing of cotton fibers and
their blends. They are also very important for the printing of regenerated cellulosic
fibers such as viscose rayon and lyocell (a special type of regenerated cellulose) where
bright shades and high wet fastness is required. The revolution in reactive dye usage has
been brought about by a steady reduction in the costs of manufacture; the cost
reductions made possible by the production of larger batch sizes and improved yields
during the coupling stage of manufacture. The principal chemical classes of reactive dyes
are azo (including metallized azo), anthraquinones, triphendioxazine, phthalocyanine
and formazan. High-purity reactive dyes are also used in the ink-jet printing of textiles,
especially cotton [1, 2].
Contrary to other dye groups, reactive dyes are characterized by known
chromophoric systems and by bearing various reactive moieties in their molecules. The
chromophoric systems include the following groups azo, anthraquinones, indigoid,
cationic dyes, polymethine, di- and triarylcarbenium, phthalocyanine, sulfur compounds,
metal complexes and fluorescent dyes. Thus, dye systems which are used to form
reactive dyes comprise all industrially important groups of dyes. Since all the dyes
synthesized in the present work have azo chromophore, which account for more than 50
% of commercial dyes, their general synthesis is discussed in the subsequent section.
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2.1.1 General Synthesis of Reactive Dyes with Azo Chromophore
Azo dyes contain at least one azo group but can contain two (disazo), three
(trisazo), or, more rarely, four (tetrakisazo) or more (polyazo) azo groups. The azo
group is attached to two groups, of which at least one, but more usually both, are
aromatic. They exist in the trans form 1 in which the bond angle is approximately 120°,
the nitrogen atoms are sp2 hybridized, and the designation of A and E groups is
consistent with colour index (CI) usage [1]. In monoazo dyes, the most important type,
the A group often contains electron-accepting substituents, and the E group contains
electron-donating substituents, particularly hydroxyl and amino groups. If the dyes
contain only aromatic groups, such as benzene and naphthalene, they are known as
carbocyclic azodyes. If they contain one or more heterocyclic groups, the dyes are
known as heterocyclic azo dyes [3].
Almost without exception, azo dyes are made by diazotization of a primary
aromatic amine followed by coupling of the resultant diazonium salt with an electron
rich nucleophile. The diazotization reaction is carried out by treating the primary
aromatic amine with nitrous acid, normally generated in situ with hydrochloric acid and
sodium nitrite. The nitrous acid nitrosates the amine to generate the N-nitroso
compound, which tautomerises to the diazo hydroxide (Eq. 1). Protonation of the
hydroxy group followed by the elimination of water generates the resonance stabilised
diazonium salt (Eq. 2). For weakly basic amines, i.e., those containing several electron-
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withdrawing groups, nitrosyl sulfuric acid (NO+HSO4-) is used as the nitrosating agent in
sulfuric acid, which may be mixed with phosphoric, acetic or propionic acid.
(1)
(2)
A diazonium salt is a weak electrophile and hence reacts only with highly electron
rich species such as amino and hydroxy compounds. Even hydroxy compounds must be
ionized for reaction to occur. Consequently, hydroxy compounds such as phenols and
naphthols are coupled in an alkaline medium (pH ≥ pKa of phenol or naphthol; typically
pH 7.11), whereas aromatic amines such as N,N- dialkylamines are coupled in a slightly
acid medium, typically pH 1.5. This provides optimum stability for the diazonium salt
(stable in acid) without deactivating the nucleophile (protonation of the amine). The
most important diazo coupling components can be divided into the following groups.
Where there are several possibilities for coupling, the preferred coupling positions are
marked by bold arrows and the other possible coupling positions by ordinary arrows
(Figure 2.1).
Figure 2.1 Coupling components
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When treated with aniline, diazotized aniline (benzenediazonium chloride) yields, apart
from a small quantity of 4-aminoazobenzene (2), diazoaminobenzene (3) as the main
product. Compound 2 is obtained by coupling in a more strongly acid medium, but
better still by heating 3 in aniline with addition of aniline hydrochloride. Electron-
donating substituents in the aniline, such as methyl or methoxy groups, especially at the
meta position, promote coupling; the tendency to couple thus increases in the order
aniline < o–toluidine < m–toluidine < m–anisidine < cresidine < 1-amino-2,5-dimethoxy
benzene to the extent that without formation of the diazoamino compound, the last
three bases are attached almost quantitatively in the desired position, i.e., at the 4-
position relative to the amino group [4-6]. m-Phenylenediamines couple to form
monoazo dyes (chrysoidines) or disazo dyes. Some of the important examples for
diazotization and coupling reactions include naphthalene-1-amine (4), 5-
aminonaphthalene-1-sulfonic acid (5), and 3-aminonaphthalene-2,7-disulphonic acid
(6).
Coupling components containing both amino and hydroxyl groups, such as H-acid
(1-amino-8-naphthol-3,6-disulfonic acid) can be coupled stepwise (Figure 2.2).
Coupling is first carried out under acid conditions to effect azo formation in the amino-
substituted ring. The pH is then raised to ionise the hydroxyl group (usually to pH 7) to
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effect coupling in the naphtholate ring, with either the same or a different diazonium
salt. Performing this process in the reverse order fails because the nucleophilicity of the
amino group is insufficient to facilitate the second coupling step. The unusual conditions
needed to produce an azo dye, namely, strong acid plus nitrous acid for diazotization,
the low temperatures necessary for the unstable diazonium salt to exist, and the
presence of electron-rich amino or hydroxy compounds to effect coupling, means that
azo dyes have no natural counterparts.
Figure 2.2 General coupling of H–Acid
Most reactive dyes fall in the category of azo dyes. Virtually every hue in the dye
spectrum can be achieved by appropriate structural modifications (mono- and disazo
dyes, combinations involving either single or multiple aromatic and heterocyclic ring
systems). Monoazo dyes with heterocyclic coupling components, such as pyrazolone or
pyridone, are yellow to greenish yellow. Other suitable coupling components include
aniline and naphthylamine derivatives. Substituted anilines or amino-naphthalene
sulfonic acids are employed as diazo components. A particularly important class of
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coupling components is the aminohydroxy-naphthalenesulfonic acids. Appropriate
variation of the diazo component permits the development of shades ranging from
orange to black. Orange and scarlet are achieved with I-acid (6-amino-1-hydroxy-
naphthalene-3-sulfonic acid) and γ-acid (7-amino-1-hydroxynaphthalene-3-sulfonic
acid), whereas H-acid (8-amino- 1-hydroxynaphthalene-3,6-disulfonic acid) and K-acid
(8-amino-1-hydroxy-naphthalene-3,5-disulfonic acid) derivatives are useful for red to
bluish-red hues. Extremely lightfast red shades are also accessible with disazo dyes
(brown dyes). H-acid is used as a double coupling component as in 7 (Reactive Black 5),
in which the reactive groups are present at both diazo functions. The synthesis of such a
reactive dye is achieved by coupling two moles of diazotized vinyl sulfone with one mole
of H-Acid at pH 1.2. The crude material is salted out of the solution and isolated. This
product gives a blue solution in water and dyes cotton in a marine blue to black colour
[2, 7, 8].
The aim of the work was to synthesize new reactive dyes having more no. of
sulfonic acid groups for greater water solubility and better color yield. With this in view
five reactive dyes Red A, Red B, Red C, Orange D and Black BE were synthesized. The
dyes contained sulfo vinylsulfone functionality and were prepared by either reacting
cyanuric chloride with H-acid and coupling with the diazotized product of sulfo
vinylsulfone/sulfo tobiaz acid or reacting diazotized sulfo vinylsulfone with H-
acid/sodium napthonate under optimized conditions. They were characterized by
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melting point, elemental analysis and 1H-NMR spectral data. Their purity was
ascertained by ion-pair reversed-phase HPLC analysis.
2.2 Materials and Instrumentation
H-acid (1-amino-8-hydroxynapthalene-3-6-disulfonic acid, 98 %) and sulfo vinyl
sulfone (4-(β-ethylsulphate)sulphonylaniline, 99.2 %) were procured from Mayur
Chemicals (Ahmedabad, India) and Atul Ltd. (Valsad, India) respectively. Cyanuric
chloride (2,4,6-trichloro-1,3,5-triazine, 98.4 %) and sodium napthonate (99.0 %) were
purchased from IDI Ltd. (Ahmedabad, India). Sodium chloride (NaCl), potassium
chloride (KCl), sodium carbonate (Na2CO3), sodium nitrite (NaNO2), trisodium
phosphate, sodium hydroxide (NaOH) and hydrochloric acid (HCl) were of commercial
grade. Analytical grade ethyl acetate and n-propanol solvents used for TLC were
obtained from Merck Specialties Pvt. Ltd. (Mumbai, India).
Thin layer chromatography was performed on pre-coated silica gel 60 F254 plates
from E. Merck (Darmstadt, Germany). Purity was determined on Shimadzu Prominence
UFLC with SPD-20A detector using BDS Hypersil C18 (250 × 4.6 mm, 5 µ particle size)
analytical column (Tokyo, Japan). The mobile phase consisted of 1.5 mM tetra-butyl
ammonium bromide in deionized water: acetonitrile (40: 60, v/v) and was delivered at a
flow rate of 1.0 mL/min. The injection volume was kept at 20 µL.
2.3 Laboratory Scale Synthesis
2.4.1 Synthesis of Reactive Red A
Step 1
Solution 1: 1 M aqueous solution of cyanuric chloride was prepared by dissolving
184.41 g in 1.0 L of ice cooled water. Solution 2: 2 M (600 g) alkaline solution of H-acid
was made by dissolving 642 g in 1.0 L water and adding 106 g sodium carbonate.
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Solution 1 was then added drop wise in to Solution 2 with continuous stirring over a
period of two hours by keeping the reaction mixture at 0-5 oC to get an intermediate
Product X (yield 97.9 %). The reaction progress was monitored by TLC using a mixture
of ethyl acetate, n-propanol and water (2:6:2, v/v/v) as the solvent system (Rf value
0.52). The reaction sequence is given in Scheme I.
Scheme I Synthesis of intermediate product of Reactive Red A
Step 2
A diazonium salt of sulfo vinyl sulfone was prepared by reaction with HCl and
NaNO2 at 0-5 oC based on standard method [9], and designated as the diazotized
product. The diazotization reaction is shown in Scheme II.
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Scheme II Synthesis of diazotized sulfo vinyl sulfone
Step 3
One mol of intermediate Product X was coupled with 2 mol of diazonium salt of
sulfo vinyl sulfone at pH 5.0-6.0 to obtain Reactive Red A dye. The solution was made
slightly alkaline with 0.1M anhydrous sodium carbonate, followed by 7 % solution of
sodium chloride and 9 % solution of potassium chloride (by volume) to harvest the dye
by salting. The solution was filtered, and the product obtained was dried and ground to
fine powder (yield, 98.2 %). The course of the reaction was monitored by TLC using a
mixture of ethyl acetate, n-propanol and water (2:6:2, v/v/v) as the solvent system (Rf
value 0.41). Molecular formula: C29H28N9O32S10Cl (1490.7 g/mol); mp: decomposes
above 216 oC. Elemental analysis: Found, C (31.36 %), H (1.82 %) and N (8.50 %);
Calculated, C (31.42 %), H (1.83 %) and N (8.46 %). 1H-NMR (400 MHz, DMSO-d6) δ:
8.900 (62, 1H, dd, J=3.552, J=1.462), 8.900 (59, 1H, dd, J=3.552, J=1.462), 8.815 (63, 1H,
dd, J=5.981, J=1.462), 8.815 (60, 1H, dd, J=5.981, J=1.462), 8.808 (15, 1H, d, J=1.251),
8.808 (13, 1H, d, J=1.251), 8.716 (29, 1H, d, J=1.266), 8.716 (24, 1H, d, J=1.266), 8.378
(80, 1H, d, J=14.930), 8.377 (81, 1H, d, J=14.921), 8.382 (30, 1H, dd, J=1.266, J=1.251),
8.382 (25, 1H, dd, J=1.266, J=1.251), 7.998 (57, 1H, dd, J=5.981, J=3.552),7.998 (55, 1H,
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dd, J=5.981, J=3.552), 7.239 (76, 1H, d, J=14.930), 7.238 (79, 1H, d, J=14.921) (Figure
2.3). The reaction with conditions is presented in Scheme III.
Scheme III Synthesis of Reactive Red A
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Figure 2.3 1H NMR spectra of Red A
2.4.2 Synthesis of Reactive Red B
Step 1
Solution 1: 1 M aqueous solution of cyanuric chloride was prepared by dissolving
184.4 g in 1.0 L of ice cooled water. Solution 2: 1 M alkaline solution of H-acid was made
by dissolving 321 g in 500 mL water and adding 53 g sodium carbonate. Solution 1 was
then added drop wise in Solution 2 with continuous stirring over a period of two hours
by keeping the reaction mixture at 0-5 oC to get intermediate product Y (yield 97.7 %).
The reaction progress was monitored by TLC using a mixture of ethyl acetate, n-
propanol and water (2:6:2, v/v/v) as the solvent system (Rf value 0.54). The reaction
sequence is given in Scheme IV.
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Scheme IV Synthesis of intermediate product of Reactive Red B
Step 2
The synthesis of diazonium salt of sulfo vinyl sulfone was identical to that
presented in Scheme II.
Step 3
One mol of intermediate product Y of Reactive Red B was coupled with 1 mol of
diazonium salt of sulfo vinyl sulfone (diazotized product, Scheme II) at pH 5.5-6.0 to
obtain Reactive Red B dye. The solution was made slightly alkaline with 0.1M anhydrous
sodium carbonate, followed by 7 % solution of sodium chloride and 9 % solution of
potassium chloride (by volume) to collect the dye by salting. The solution was filtered,
and the product obtained was dried and ground to fine powder (yield, 97.9 %). The
course of the reaction was monitored by TLC using a mixture of ethyl acetate, n-
propanol and water (2:6:2, v/v/v) as the solvent system (Rf value 0.43). Molecular
formula: C21H14N6O16S5Cl2 (837.5 g/mol); mp: decomposes above 182 oC. Elemental
analysis: Found, C (30.20 %), H (1.65 %) and N (9.88 %); Calculated, C (30.11 %), H
(1.68 %) and N (10.03 %). 1H-NMR (400 MHz, DMSO-d6) δ:8.900 (35, 1H, dd, J=3.552,
J=1.462), 8.815 (36, 1H, dd, J=5.981, J=1.462), 8.716 (18, 1H, d,J=1.266),8.707 (12, 1H, d,
J=1.251), 7.999 (19, 1H, dd, J=1.266, J=1.251), 7.680(33, 1H, dd, J=5.981, J=3.552), 7.478
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(45, 1H, d, J=14.930), 7.440 (44, 1H, d, J=14.930). The reaction with conditions is
presented in Scheme V.
Scheme V Synthesis of Reactive Red B
Figure 2.4 1H NMR spectra of Red B
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2.4.3 Synthesis of Reactive Red C
Step 1
This step was similar to the one shown in Scheme IV (Product Y).
Step 2
A diazonium salt of sulfo tobiaz acid was prepared by reaction with HCl and NaNO2
at 0-5 0C based on standard method [9], and designated as diazotized product of sulfo
tobiaz acid. 1 mol of intermediate product of Reactive red C (Product Y) was reacted
with 1 mol of diazonium salt of sulfo tobiaz acid at pH 5.5-6.0 to give dichloro triazine,
product Z (Scheme VI).
Scheme VI Synthesis of dichloro triazine, product Z.
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Step 3
The product Z was then coupled with sulfo vinyl sulfone at 40-45 oC by
maintaining the pH between 5.0-5.5. The solution was subsequently made slightly
alkaline with 0.1M anhydrous sodium carbonate, followed by 7 % solution of sodium
chloride and 9 % solution of potassium chloride (by volume) to harvest the dye by
salting. The solution was filtered, and the product obtained was dried and ground to fine
powder(yield, 97.2 %). The reaction is presented in Scheme VII.
Scheme VII Synthesis of Reactive Red C.
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Figure 2.5 1H NMR spectra of Red C
2.4.4 Synthesis of Reactive Orange D
Step 1
The synthesis of diazonium salt of sulfo vinyl sulfone was identical to that
presented in Scheme II.
Step 2
The diazonium salt of sulfo vinyl sulfone was added drop wise with stirring to a
solution of 1.0 M sodium napthonate, by maintaining pH 5.0-6.0 using sodium
bicarbonate at a temperature of 5-10 oC. The dye was separated from the solution by
salting out using 7% sodium chloride and 9% potassium chloride (by volume). The
product was filtered and buffered to a pH of 7.0±0.2, and finally dried to fine powder
(yield, 98.4 %). The process was monitored by TLC using a mixture of ethyl acetate, n-
propanol and water (1:6:2, v/v/v) as the solvent system (Rf value 0.56). Molecular
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formula: C18H15N3O12S4 (593.5 g/mol); mp: decomposes above 167 oC. Elemental
analysis: Found, C (36.22 %), H (2.48 %) and N (7.02 %); Calculated, C (36.42 %), H
(2.55 %) and N (7.08 %). 1H-NMR (400 MHz, DMSO-d6) δ:8.889 (26, 1H, ddd, J=2.797,
J=1.758, J=0.847), 8.823 (13, 1H, dd, J=1.758, J=1.535), 8.657 (14, 1H, dd, J=6.183,
J=1.758), 8.630 (7, 1H, d, J=14.951), 8.614 (27, 1H, dd, J=6.383, J=1.758), 7.669 (29, 1H,
ddd, J=6.383, J=5.373, J=2.797), ), 7.659 (35, 1H, dd, J=7.890, J=5.373)7.402 (33, 1H, dd,
J=7.890, J=0.847), 7.174 (16, 1H, dd, J=6.183, J=1.535), 7.158 (8, 1H, d, J=14.951. The
reaction is presented in Scheme VIII.
Scheme VIII Synthesis of Reactive Orange D.
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Figure 2.6 1H NMR spectra of Orange D
2.4.5 Synthesis of Reactive Black BE
Step 1
The synthesis of diazonium salt of sulfo vinyl sulfone was identical to that
presented in Scheme II.
Step 2
An alkaline solution (0.5 M) of H-acid was prepared by dissolving 160.5 g in 250 mL
water and adding 26.5 g sodium carbonate. A 1.0 M diazotized sulfo vinyl sulfone was
then coupled with 0.5 M H-acid solution maintained at pH 2.0-3.0 and 0-5 oC
temperature. The dye was separated from the solution by salting out with the use of 7%
sodium chloride and 9% potassium chloride (by volume), then filtered and buffered to a
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pH of 7.0±0.2, and finally dried (yield, 99.2%). The process was monitored by TLC using
a mixture of ethyl acetate, n-propanol and water (1:6:2, v/v/v) as the solvent system (Rf
value 0.38). Molecular formula: C26H21N5O25S8 (1059.8 g/mol); mp: decomposes above
171 oC. Elemental analysis: Found, C (29.21 %), H (2.02 %) and N (6.65 %); Calculated, C
(29.46 %), H (2.00 %) and N (6.61 %). 1H-NMR (400 MHz, DMSO-d6) δ: 8.911 (50, 1H,
dd, J=4.124, J=1.462), 8.636(12, 1H, dd, J=5.973, J=1.461), 7.985 (13, 1H, dd, J=5.970,
J=1.462), 7.911 (49, 1H, dd, J=4.141, J=1.461), 7.695 (29, 1H, d, J=1.446), 7.691 (37, 1H,
d, J=1.446),7.353 (6, 1H, d, J=15.012), 7.351 (59, 1H, d, J=14.999)7.331 (47, 1H, dd,
J=5.973, J=4.141), 7.244 (15, 1H, dd, J=5.970, J=4.124), 7.243 (58, 1H, d, J=14.999), 7.142
(7, 1H, d, J=15.012). The reaction sequence is given in Scheme IX.
Scheme IX Synthesis of Reactive Black BE
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Figure 2.7 1H NMR spectra of Black BE
2.4 Scaled-up Synthesis for Manufacturing Plant
During the second part of the study, scaled-up laboratory synthesis of dyes to the
manufacturing scale was initiated. The basic steps of dye and intermediate
manufacturing involved the following operation sequence, material charging
reaction product isolation product drying grinding finishing. There are
usually several reaction steps or unit processes. The reactor itself, in which the unit
processes to produce the intermediates and dyes are carried out, is usually the focal
point of the plant for manufacture. Figure 2.8 shows a block diagram of the dye
manufacturing plant.
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Figure 2.8 Block diagram of the dye manufacturing plant
A bomb-shaped rubber line reaction vessel, made from cast iron was used to
conduct the reactions for the production of intermediates and dye. The capacities of
these vessels were 15000 L (8.5 × 10 feet) and were equipped with mechanical
agitators, pH and temperature probes and condensers. The aqueous solutions were
heated by direct introduction of steam through a boiler, and cooling was done by
addition of ice. The reaction vessels spanned two floors in the plant to facilitate ease of
operation. Products are transferred from one piece of equipment to another by gravity
flow, in filter boxes, on continuous belt filters. The presses are dressed with cloths of
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cotton, while separate channels were provided for efficient washing. To increase the
solid content of the press cake, hydraulic squeezing was carried out. The plates and
frames are made of cast iron.
Unlike lab scale synthesis, all the intermediates used for scaled-up synthesis of
reactive dyes for manufacturing plant were of industrial grade. The % purity of the raw
materials was H-acid (80 %), sulfo vinyl sulfone (70 %), cynuric chloride (99.0 %), sulfo
tobiaz acid (80 %) and sodium napthonate (90 %). They were used without further
purification/processing to avoid handling loss and to minimize the overall cost. For a
typical commercial batch size, the amount of raw material used and the dye yields
obtained are summarized in Table 2.1.
Table 2.1 Summary of scaled-up synthesis of reactive dyes
Dye Raw materials ReactionYield
Product quality
Reactive Red A
H-acid (800 kg)
Sulfo vinyl sulfone
(1030 kg)
Cyanuric chloride (185 kg) 1666 kg Good
Reactive
Red B
H-acid
(400 kg)
Sulfo vinyl
sulfone (515 kg)
Cyanuric chloride
(185 kg)
925 kg
Good
Reactive
Red C
H-acid
(400 kg)
Sulfo
tobiaz acid (280 kg)
Cyanuric chloride (185 kg)
Sulfo vinyl
sulfone (515 kg)
1236 kg
Good
Reactive Orange D
Sodium napthonate
(272 kg)
Sulfo vinyl sulfone
(515 kg)
638 kg
Good
Reactive Black BE
H-acid (400 kg)
Sulfo vinyl sulfone
(1030 kg)
1192 kg
Good
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2.5 Purity Assessment of Dyes by HPLC
The purity of the synthesized dyes was assessed by ion-pair reversed-phase high
performance liquid chromatography (RP-HPLC). Initially, several reversed-phase
columns like Phenomenex Gemini C18 (150/250 mm x 4.6 mm, 5 µm), Waters Atlantis
T3 C18 (150/250 mm x 4.6 mm, 5 µm), Thermo Hypurity C18 (150 mm x 4.6 mm, 5 µm),
ACE C18 (150 mm x 4.6 mm, 5 µm) and BDS Hypersil C18 (250 mm × 4.6 mm, 5 µm)
were tried to optimize the chromatographic conditions for adequate retention and peak
shape. Further, acetate and phosphate buffers together with organic modifiers like
methanol and acetonitrile were also tested. However, all attempts for efficient
chromatographic separation were largely unsuccessful with regard to adequate
retention and peak separation. Thus, use of ion-pairing agent like tetra-butyl ammonium
bromide in water was tried in combination with methanol and acetonitrile in different
volume ratios. After many trials, all five dyes and their raw materials were successfully
chromatographed on a BDS Hypersil C18 (250 mm × 4.6 mm, 5 µm) analytical column
using 1.5 mM tetra-butyl ammonium bromide in deionized water: acetonitrile (40: 60,
v/v) as the mobile phase. Under the optimized chromatographic conditions, the
observed retention time for the raw materials (Figure 2.9) and dyes (Figure 2.10)
were H-acid (7.797 min), sulfo vinyl sulfone (11.572 min), sodium napthonate (2.113
min), sulfo tobiaz acid (2.603 min), 16.675 min (Red A), 6.133 min (Red B), 9.477 min
(Red C), 4.463 min (Orange D) and 6.340 min (Black BE). The purity of the dyes as
determined from their peak areas analysis was 99.2, 98.7, 98.2, 98.8 and 99.4 % for Red
A, Red B, Red C, Orange D and Black BE respectively.
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Figure 2.9 HPLC chromatograms of raw materials
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Figure 2.10 HPLC chromatograms of synthesized reactive dyes
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2.6 Conclusions
Five new reactive dyes containing azo chromophores and possessing more
number of sulfonic acid groups were synthesized for greater water solubility and better
color yield. The dyes contained sulfo vinyl sulfone functionality and were prepared by
reacting either cyanuric chloride with H-acid and coupling with the diazotized product
of sulfo vinyl sulfone/sulfo tobiaz acid or reacting diazotized sulfo vinyl sulfone with H-
acid/sodium napthonate under optimized experimental conditions. All the dyes were
obtained in quantitative yields and had purity > 98 % as ascertained from HPLC analysis.
Additionally, scaled-up synthesis of the dyes was also carried out for a typical
manufacturing plant with acceptable efficiency and yield.
2.7 References
[1] S.M. Fergusson, Master’s Thesis, Diploma Textile Industries, RMIT University,
Leeds, 2008.
[2] K. Hunger (Ed.) Industrial Dyes: Chemistry, Properties, Applications, Wiley-VCH,
Verlag GmbH and Co., Weinheim, Germany, 2003, Chapter 1, pp. 1-12.
[3] P. F. Gordon, P. Gregory, Organic Chemistry in Colour, Springer-Verlag, Berlin,
1983.
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[4] A. Calder, Dyes in Non-Impact Printing, IS and T’s Seventh International Congress
on Advances in Non-Impact Printing Technologies, Portland, Oregon, 1991.
[5] G. Booth, The Manufacture of Organic Colorants and Intermediates, Society of
Dyers and Colourists, Bradford, UK, 1988.
[6] P. Gregory in The Chemistry and Application of Dyes (Eds.: D. R.Waring, G. Hallas),
Plenum, New York, 1990, pp. 17-47.
[7] Colour Index, Vol. 4, 3rd ed., The Society of Dyers and Colourists, Bradford, UK,
1971.
[8] P. Gregory, High Technology Applications of Organic Colorants, Plenum, New York,
1991.
[9] A.I. Vogel, A.R. Tatchell, B.S. Furnis, A.J. Hannaford, P.W.G. Smith, Vogel’s Textbook
of Practical Organic Chemistry, 5th Edition, Prentice Hall, London, England, 1996.